The present invention relates to an internal routing method in the internal network for improving signaling message processing capability by balancing the workload among message handling processor(MHP) in common channel signaling(CCS) system used in electronic exchanges.
Description of the prior art with reference to FIG. 1-3 will be shown hereinafter.
FIG. 1 illustrates relations between CCITT NO. 7 functional level structures and OSI(Open System Interconnection) layers. In common channel signalling CCITT NO. 7, there are level 1 signaling data link functions, Level 2 signaling Link functions, Level 3 signaling network functions and level 4 user part functions. The user part functions are largely divided into functions of essential parts for applications, ISDN user part functions, and telephone user part functions, which are shown in comparison with 7 layers proposed by OSI in this figure. An arrangement for performing such common channel signalings may take its own structure depending on the types of realizations.
FIG. 2 illustrates diagrammatically the configuration of a common channel signaling system in electronic exchanges. This system comprises signaling data links for performing the level 1 functions, signaling terminals(ST) for performing level 2 functions, message handling processors for performing level 3 functions and user part processors for performing level 4 functions. Also, this system comprises a message transfer network(MTN) providing communication paths between signaling terminals and message handling processors, and a control interworking network(CIN) providing communication paths between user part processors and message handling processors.
Thus all of the signaling terminals and all of the user part modules can communicate with any message handling processors through these networks.
In the system of FIG. 2, the signaling terminals receive the signaling messages from remote exchanges through the signaling data Link, and after processing the level 2 protocol, and send the received signaling messages are sent to the message handling processors via the message transfer network. The message handling processors send these signaling messages to the user part processors via the control interworking network after performing the signaling message handling functions of the level 3 protocol. On the other hand, the signaling messages generated from the user parts of the own exchange are sent to the message handling processors via the control interworking network. The message handling processors send these signaling messages to the signaling terminals via the message transfer network after performing the level 3 protocol, and the signaling terminals transmit them to the remote exchange through the signaling data link.
The routing from the message handling processors to the user parts in the incoming routing for signaling messages from the remote exchange, and the routing from the message handling processors to the signaling terminals in the outgoing routing for signaling messages to the remote exchange are performed on the basis of the specification of the CCITT No. 7 protocols. However, proper methods may be applied to the routing from the signaling terminals to the message handling processors in incoming routing and to the routing from the user parts to the message handling processors in outgoing routing.
Thus, the routing from the signaling terminals to the message handling processors and from the user parts to the message handling processors may be performed by optionally established methods, and allotment of load to the message handling processors also may be achieved by means of these methods. Although a simple method may be utilized in which routing can be achieved by optionally associating the message handling processors with the respective user parts or with the signaling terminals, such a method has a problem that it is difficult to equally assign the traffic load to the message handling processors in the case that there are failed message handling processors. Also, in the existed routing methods, when successive failures of the message handling processors occurred, the system exhibits centralization of load, thereby degrading the performances of the message handling processors. Consequently, the degree of uniform distribution of load has great influence on the performances of the message handling processors, and hence on the total performance of the common channel signaling system.
Hereinafter, the descriptions of an approach for obtaining the limiting curve of MHP processing capacity affected by the load unbalancing and as to the influencing of the load unbalancing on the signaling message processing capacity of the common channel signaling system will be shown.
Define the following parameters:
v: ratio of available message service time to total CPU time in MHP, PA0 .lambda.: total workload of CCS system (messages/second) PA0 N: number of MHP's in CCS system PA0 r: unbalance factor (ratio of peak to average workload in each stage) PA0 s: mean service time of MHP
Since MHP generally consists of a processor and I/O device such as DMA(Direct Memory Access), the equation for the approximated mean service time S can be expressed as follows EQU S=2(CT.sub.I +BT.sub.D /U)+T.sub.P ( 1)
where
C: Number of instructions for DMA initialization, PA1 T.sub.I : Average execution time per instruction, PA1 B: Mean message length(bits) PA1 T.sub.D : DMA data transfer time per unit data PA1 U: Unit data length(bits) PA1 T.sub.P : Protocol processing time per message by CPU
The limiting curve of MHP processing capacity depends upon mean service times of MHP and MHP with unbalanced traffic has the total workload of r.lambda.N. Thus, we can denote the message service time V as (s)(r.lambda./N). In equation(1), the mean length B can be substituted by R/.lambda., where, R is the maximum bit rates of MHP. Hence, EQU V=(r.lambda./N)[2(CT.sub.I +(R/.lambda.)T.sub.D /U)+T.sub.P ],
which, after rearrangement with respect to the R, becomes EQU R=0.5UVN/(rT.sub.D)-.lambda.U(CT.sub.I +0.5T.sub.P)T.sub.D ( 2)
FIG. 3 shows the limiting curve in the case that 16 message handling processors (M=16) are used in the common channel signaling system. In FIG. 3, the number .lambda. of message corresponding to X coordinate of the point in which the line representing mean message length intersects the limiting curve, results in threshold of MHP processing capacity. For the numerical analysis, we assume that the target configuration has the following parameter values: T.sub.I =1.8 .mu.s, T.sub.D =2.75 .mu.s, T.sub.P =0.2 ms, C=10, U=8, V=0.6. In this figure, the message processing capacity is about 28,000 messages per second for the perfect balanced workload (r=1) configuration and the mean message length of 15 octets which estimated for telephone application. In case of the unbalanced workload (r=1.4), however, the message processing capacity is less than 20,000 messages per second. Therefore, the load balancing is very important for the system performance.